Engine starter gearing



J. E. BUXTON.

' ENGINE STARTER GEARING Filed Nov. 13, 1942 I April 4, 1944.

Patented Apr. 4, 1944 UNITED STATES PATENT OFFICE ENGINE STARTER GEARINGJames E. Buxton, Elmira, N. Y., assignor to Bendix Aviation Corporation,South Bend, Ind., a corporation of Delaware Application November 13,1942, Serial No. 465,491

2 Claims.

The present invention relates to engine starter gearing and moreparticularly to a starter drive of the type in which a motor drivenpinion is held in mesh with an engine gear until a successful start issecured.

Starters of this type have been developed that use a latching mechanismto hold the pinion in mesh, which latch is controlled by variouscentrifugal devices. These arrangements are more or less specializedaccording to the particular type of control adopted.

It is an object of the present invention to provide a novel starterdrive in which the pinion is held in mesh with the engine gear by alatch which is normally engaged, and is disengaged when the startingmotor attains a predetermined rotative speed.

It is another object to provide such a device in which the pinion isdriven from the starting motor through an overrunning clutch so that theacceleration of the pinion by the engine gear when the engine fires isnot transmitted back to the starting motor.

Further objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation partly in section of a preferred embodimentof the invention;

Fig. 2 is a section taken substantially on the line 2-2 of Fig. l; and

Fig. 3 is a view similar to Fig. 2 showing the parts in latchedposition.

In Fig. 1 of the drawing there is illustrated a power shaft l which maybe the extended armature shaft of a starting motor not illustrated. Thepower shaft is provided with an extended portion 2 of reduced diameterproviding a stop shoulder 3 forming a seat for a thrust ring 4. A screwshaft 5 is fixed on the outer end of the power shaft by suitable meanssuch as a cross pin 6, and a pinion I is slidably journalled on thepower shaft adjacent the end of the screw shaft for movement into andout of mesh with a gear 8 of the engine to be started.

A nut member 9 is threaded on the screw shaft, and a yielding drivingconnection from the nut to the pinion including an overrunning clutch isprovided in order to translate the pinion on the power shaft andtransmit rotation thereto to crank the engine. As here shown, thisyielding driving connection comprises a cylindrical block ll ofelastically deformable material such as rubber seated on the nut 9 andbearing against a radial flange l2 thereof. A barrel I3 surrounds theblock ll, bearing at one end on the flange I2 and having a drivingclutch member i4 fixed in its other end in any suitable manner asindicated at l5. Clutch member It is provided with ratchet teeth 16arranged to engage with corresponding teeth I! on a driven clutch memberl8 fixed to the pinion 1. Yielding means for engaging the ratchet teethl6, H is provided in the form of a spring l9 mounted on the extended hub2| of the pinion l and maintained under initial compression by means ofa thimble 22 fixed on the end of said hub.

Means are preferably provided for enclosing the interior of the block llso as to prevent any products of abrasion thereof from becomingdeposited on the threads of the screw shaft. As here shown, this isaccomplished by means of a sleeve 23 seated in the driving clutch memberl4 and bearing slidably on the nut 9.

According to the present invention means are provided for holding thepinion in mesh with the engine gear until the starting motor hasattained a predetermined rotative speed. As shown in Fig. 2, a latchplunger 24 is mounted in the nut member 9, and is pressed intoengagement with the screw shaft by means of a spring 25. The screw shaftis provided with a notch 20 (Fig. 3) adapted to be engaged by the end ofthe latch when the pinion is in mesh with the engine gear so as toprevent the nut from movin the pinion out of mesh. A centrifugal member26 is pivoted at 2! to the nut and has at its free end a slidingconnection 28 with the latch in order to withdraw the latch when thestarting motor rotates the nut at a predetermined speed.

In operation, starting with the parts as illustrated in Fig. 1, rotationof the power shaft by the starting motor is transmitted to the screwshaft 5 whereby the nut 9 and its associated parts are translated alongthe power shaft, causing the pinion 1 to mesh with the engine gear 8until the pinion engages the thrust collar 4. Rotation of the powershaft is then transmitted through the yielding member I l and clutchmembers l4, l8 to the pinion to crank the engine. At this time, thelatch 24 is held in engagement with the notch 20 in the screw shaft soas to lock the pinion in meshed position. When the engine fires, theacceleration of the engine gear causes the pinion to overrun the drive,threading the nut 9 back along the screw shaft 5 until latch 24 engagesin notch 20. At this time the clutch members [4, l8 are free todisengage and overrun, thus permitting the pinion to be rotated freelyby the engine gear. If the engine does not continue to beself-operative, the cranking operation will be resumed as soon as thepinion I attains a rotative speed corresponding to that of the enginegear. When a successful start has been secured, the release of thecranking load from the starting motor permits the power shaft toaccelerate to a predetermined speed, higher than normal cranking speed,which enables the centrifugal member 26 to withdraw the latch 24 fromits engagement in notch 20 of the screw shaft. The frictional torquetransmitted from the pinion I through the overrunning clutch members isthen sumcient to cause the nut to be moved back to idle positionon thescrew shaft, and when the starting motor is de-energized, the parts areyieldably retained in idle position by the frictional engagement of thelatch 24 on the screw shaft acting as an anti-drift detent.

Although but one embodiment of the invention is described and shown indetail, it will be understood that other embodiments are possible andthat various changes may be made in the design and arrangement of theparts without departing from the spirit of the invention as defined inthe claims appended hereto.

What is claimed is:

1. In an engine starter drive a power shaft, a pinion slidablyjournalled thereon to engage and drive an engine gear, means foractuating the pinion including a screw shaft fixed to the power shaft, anut on the screw shaft, and a yielding over-running driving connectionbetween the nut and pinion, alatch on the nut normally engaging thescrew shaft and friotionally resisting rotation of the nut therein, saidscrew shaft having a notch adapted to receive the latch when the pinionis meshed with the engine gear, and centrifugal means on the nut forwithdrawing the latch.

2. In an engine starter drive a power shaft, a screw shaft fixedthereon, a pinion slidably journalled on the power shaft, a nut threadedon the screw shaft, yielding driving means con-

